We might harvest the Earth’s heat while trapping carbon emissions

It might be possible to combine carbon capture and storage with geothermal …

Geothermal power has long been touted as a valuable piece of a renewable energy portfolio, but, like other energy technologies, it has its limitations. At geothermal power plants, water is injected into warm regions of the crust and the steam that returns to the surface is used to drive a generator. As such, it requires areas with high temperatures at shallow depths (less than 3 kilometers)—that is, places where magma exists relatively close to the surface. That's not a problem for places like Iceland, but it excludes the vast majority of the United States.

In addition, geothermal power plants normally require hydraulic fracturing of the bedrock in order to create the necessary flow paths for water, which means that the amount of rock available to exchange heat with the water is limited by the extent of the fractures. On top of that, the injection of water at high pressure into those fractures has been known to trigger seismic activity, leading to controversy at some sites.

A recent paper in Geophysical Research Letters offers a creative alternative which piggybacks geothermal energy production on carbon capture and storage to boost the value of both, taking a shot at two birds with one precisely engineered stone.

The researchers used a computer model to evaluate the potential of CO2 as a heat exchange fluid for geothermal energy generation. This in itself is not a new idea, but they put a pragmatic twist on it: instead of simply replacing water with CO2 in a traditional hydraulically fractured rock system, they propose using it in lower-temperature environments at carbon capture and storage sites.

One approach to carbon capture and storage is to inject CO2 (in a liquid-like supercritical state) into deep aquifers that are capped by an impermeable layer of rock, safely locking it away. These aquifers are too deep to be economically viable sources of drinking water, and the water is too "salty" (due to high concentrations of dissolved minerals) to be desirable anyway. Rather than being a network of fractures, these aquifers are highly porous and permeable—composed of rocks like sandstone, for example—and can easily accept and hold large volumes of fluid. Fluids injected into these layers have a much larger surface area to interact with than hydraulically fractured systems do, and there's no risk of triggering earthquakes.

Once the CO2 is injected into the aquifer and allowed to pick up heat, some would be pumped back up to drive a generator before being returned. All the CO2 would still end up in the storage aquifer, but some would be used to extract heat energy along the way.

This design turns out to be pretty advantageous. For starters, CO2 can effectively transfer heat at much lower temperatures than water. Plus, their design can extract heat 3 to 5 times faster than traditional water-based systems. The researchers calculate that the amount of energy generated using water in an aquifer at 100°C (which is widely considered the lower limit for current technology) can be generated using CO2 at about 66°C. This ability to work efficiently at lower temperatures opens up a large area of the US to geothermal energy production.

Carbon capture and storage takes a fair amount of energy, so at a power plant, for example, extra fuel has to be burned to power the process. The end result is a loss of efficiency at the plant. In this coupled design, the energy produced from the geothermal system helps offset the fuel cost of carbon capture and storage. Or you can look at it the other way around—once a price is put on carbon emissions, the capture and storage side of the design will generate money, which will make the price of geothermal energy even more economically competitive.

Of course, carbon capture and storage is not a mature technology, and it still has considerable baggage in the form of debate about unknowns: How completely will the CO2 be sealed underground—will some escape? How will the CO2 fluid react with minerals in the rock? Where will the displaced “salty” water in the aquifer move to? Could drinking water aquifers be affected in any way? We'll need better answers to these questions before this technique can be widely implemented, but coupling it with geothermal energy production may move it one step towards practicality.

I'm not sure how I understand how it could be a net gain. Once we use the hot CO2, we have to re-compress it to replenish it. That seems energy neutral. Given that CO2 is gaseous at STP, I don't know why you can't just do all that at the surface. I get that geothermal heats it for you, for free, but to replenish it, you have to perform an equivalent cooling to get it back down there. Don't you?

I have this little voice in the back of my head asking what happens when a gazillion tons of liquid CO2 turn into gaseous CO2. You sort of have a hydrofracting environment in an aquifer with bad but deeply buried water. Hmmmm.

On the bright side pumping carbon into an underground aquafer will make a weak acid (carbonic acid) that will dissolve the limestone slowly (then again depends how much carbon we're pumping which speeds up the whole thing) so we will be making fantastic limestone caves that we would likely never see.

Once we use the hot CO2, we have to re-compress it to replenish it. That seems energy neutral. Given that CO2 is gaseous at STP, I don't know why you can't just do all that at the surface. I get that geothermal heats it for you, for free, but to replenish it, you have to perform an equivalent cooling to get it back down there.

Not all geothermal designs necessarily require the transport fluid to transform to gas (water to steam). The liquid CO2, under pressure, can "rob" heat from cooler regions, deliver that to the surface, be piped through a heat transfer to heat some other medium... and the cooler (but still liquid) CO2 is reinjected underground.

It's "boiling point" is 150C less than water (-57). That means injecting -100 degree liquid CO2 into the ground, and pulling out 50 degree (but under pressure, thus still liquid) is a delta of 150 degrees of heat transfer capability. Possibly better than water.

Disclaimer: through I've worked in the power industry, it was in the IT department on the systems that ran the power market. Thus, I know only high school/college/amature physics w.r.t geothermal. Please don't laugh if I am that far wrong!

The carbon capture argument seems like ruminant's poo: The system is described as a close loop, so once you pumped the aquifer full of CO2, you probably don't need the resources of a carbon emitting plant anymore, just a minimum amount to replace losses.

Has any study been made on life in these high pressure saline environments, like bacteria, etc.? It looks like these scientists are just about to go plundering on natural resources without a regard for consequences.

I have this little voice in the back of my head asking what happens when a gazillion tons of liquid CO2 turn into gaseous CO2. You sort of have a hydrofracting environment in an aquifer with bad but deeply buried water. Hmmmm.

I suppose the hope is that we won't trigger a disaster like this, only on a much larger scale. Sure it is a bit further down, but I am far from convinced that millions of tons of CO2 injected into the ground will stay put indefinitely.

Also, the value of the water should not be dismissed, just because it is not economical to extract today. Water can be easily desalinated using the rejected waste heat of a LFTR or other high temperature reactor.

Perhaps it is a workable idea, but it should be very carefully considered. This is exactly the sort of thing that we shouldn't be rushing to implement now that it is crunch time. That goes for other renewables as well, which require vast areas of land and immense resources, with poorly understood impact on the environment.

It is actually VERY hard to seal Carbon Dioxide underground. It is even, I'm told, actually corrosive to material typically used to seal old oil wells. So the best way to put it anywhere is still to grow trees...

It is actually VERY hard to seal Carbon Dioxide underground. It is even, I'm told, actually corrosive to material typically used to seal old oil wells. So the best way to put it anywhere is still to grow trees...

It's not actually that difficult. All over the world, there are natural co2 formations that have held gas for millions of years. Also, there are thousands of sites with other gases, like natural gas. Of course, any site has to be studied carefully before gas injection.

The carbon capture argument seems like ruminant's poo: The system is described as a close loop, so once you pumped the aquifer full of CO2, you probably don't need the resources of a carbon emitting plant anymore, just a minimum amount to replace losses.

Has any study been made on life in these high pressure saline environments, like bacteria, etc.? It looks like these scientists are just about to go plundering on natural resources without a regard for consequences.

Correct on the first point, a developed system will need only minimal additional co2.

Many scientists are examining the impact on life. It happens that much deep subsurface life is carbon limited, so co2 injection could lead to biological growth.

I have this little voice in the back of my head asking what happens when a gazillion tons of liquid CO2 turn into gaseous CO2. You sort of have a hydrofracting environment in an aquifer with bad but deeply buried water. Hmmmm.

At deep underground conditions, co2 will never become a gas but will remain a relatively dense liquid-like fluid. Also, in any deep injection where you don't want fracturing, you make sure to inject well below the fracture threshold, which is relatively easy with co2 compared to many other commonly injected fluids.

"Where will the displaced “salty” water in the aquifer move to? Could drinking water aquifers be affected in any way?"

As a lay person to this field, I think more generally that injecting anything into the earth will probably result in something else coming out/up. That's good for geothermal energy farming, but not for carbon storage.

Once we use the hot CO2, we have to re-compress it to replenish it. That seems energy neutral. Given that CO2 is gaseous at STP, I don't know why you can't just do all that at the surface. I get that geothermal heats it for you, for free, but to replenish it, you have to perform an equivalent cooling to get it back down there.

Not all geothermal designs necessarily require the transport fluid to transform to gas (water to steam). The liquid CO2, under pressure, can "rob" heat from cooler regions, deliver that to the surface, be piped through a heat transfer to heat some other medium... and the cooler (but still liquid) CO2 is reinjected underground.

It's "boiling point" is 150C less than water (-57). That means injecting -100 degree liquid CO2 into the ground, and pulling out 50 degree (but under pressure, thus still liquid) is a delta of 150 degrees of heat transfer capability. Possibly better than water.

Disclaimer: through I've worked in the power industry, it was in the IT department on the systems that ran the power market. Thus, I know only high school/college/amature physics w.r.t geothermal. Please don't laugh if I am that far wrong!

(edit: forgot negative sign)

Consider the Pressurized Water Reactor nuclear plant. Liquid water is circulated between the nuclear reactor and the "steam generator", where the heat is transferred to a second water loop, one that does turn to steam, rotate a turbine, and cool back to water. The first water loop is always liquid all the time.

"Where will the displaced “salty” water in the aquifer move to? Could drinking water aquifers be affected in any way?"

As a lay person to this field, I think more generally that injecting anything into the earth will probably result in something else coming out/up. That's good for geothermal energy farming, but not for carbon storage.

Generally, the amount of fluid injected is very small compared to the volume of the formations. So, the displaced water can be accomodated by slight pressure increases through a large reservoir volume, among other things.

Some of the nice places to inject co2 are depleted, partially "empty" oil and natural gas formations. There, we know the geology has the space for injected fluid and can hold fluid for millions of years.

It is actually VERY hard to seal Carbon Dioxide underground. It is even, I'm told, actually corrosive to material typically used to seal old oil wells. So the best way to put it anywhere is still to grow trees...

Jah, the whole carbon sequestration thang always did strike me as horseshit. First because it will leak, but more importantly, because the storage area wont even come close to the volume of co2 generated at today's massive scales, and especially because it would cost a fortune.

Totally agree with the previous commenter that the co2 in this case is a red Herring, being little more than a transfer fluid of limited and fixed quantity.

I have this little voice in the back of my head asking what happens when a gazillion tons of liquid CO2 turn into gaseous CO2. You sort of have a hydrofracting environment in an aquifer with bad but deeply buried water. Hmmmm.

I suppose the hope is that we won't trigger a disaster like this, only on a much larger scale. Sure it is a bit further down, but I am far from convinced that millions of tons of CO2 injected into the ground will stay put indefinitely.

Also, the value of the water should not be dismissed, just because it is not economical to extract today. Water can be easily desalinated using the rejected waste heat of a LFTR or other high temperature reactor.

Perhaps it is a workable idea, but it should be very carefully considered. This is exactly the sort of thing that we shouldn't be rushing to implement now that it is crunch time. That goes for other renewables as well, which require vast areas of land and immense resources, with poorly understood impact on the environment.

Salty water deep underground is way more salty than seawater, so we would desalinate seawater before we would ever use deep aquifer water. On the last year, there have been studies on the economics of deep aquifer desalination.

I have this little voice in the back of my head asking what happens when a gazillion tons of liquid CO2 turn into gaseous CO2. You sort of have a hydrofracting environment in an aquifer with bad but deeply buried water. Hmmmm.

At deep underground conditions, co2 will never become a gas but will remain a relatively dense liquid-like fluid. Also, in any deep injection where you don't want fracturing, you make sure to inject well below the fracture threshold, which is relatively easy with co2 compared to many other commonly injected fluids.

I have always shared alternety's concern. While the elevated pressures under ground can keep the CO2 in liquid form, my concern is that eventually, some release of that that pressure would allow CO2 to suddenly return to gas form.

The EPA maintains that "Confidence in this technology is supported by the knowledge that CO2 produced through natural processes has been retained in geologic formations for hundreds of millions of years (IPCC, 2005). The presence of multiple trapping mechanisms will reduce the mobility of CO2 underground over time, decreasing the risk of CO2 leaking to the surface (IPCC, 2005). It is likely that well-selected, well-designed, and well-managed GS sites can sequester CO2 for long periods of time."

I suppose that the selected sites are carefully screen to prevent this, but I still don't see this as a permanent solution for geological time-scales. Some recent research papers suggest that we would need a much larger storage volume/CO2 volume ratio to prevent a Lake Nyos-type catastrophe, so our current estimates and degree of certainty may be off target.

Since the IPCC estimates that we can store 1,100,000 megatons of CO2 underground, I simply cannot see how we can be certain that catastrophic out-gassing amounts of only ~1 megaton will never happen.

Now, whether this risk is worth taking to help attenuate climate change is another story altogether...

I have this little voice in the back of my head asking what happens when a gazillion tons of liquid CO2 turn into gaseous CO2. You sort of have a hydrofracting environment in an aquifer with bad but deeply buried water. Hmmmm.

At deep underground conditions, co2 will never become a gas but will remain a relatively dense liquid-like fluid. Also, in any deep injection where you don't want fracturing, you make sure to inject well below the fracture threshold, which is relatively easy with co2 compared to many other commonly injected fluids.

I have always shared alternety's concern. While the elevated pressures under ground can keep the CO2 in liquid form, my concern is that eventually, some release of that that pressure would allow CO2 to suddenly return to gas form.

The EPA maintains that "Confidence in this technology is supported by the knowledge that CO2 produced through natural processes has been retained in geologic formations for hundreds of millions of years (IPCC, 2005). The presence of multiple trapping mechanisms will reduce the mobility of CO2 underground over time, decreasing the risk of CO2 leaking to the surface (IPCC, 2005). It is likely that well-selected, well-designed, and well-managed GS sites can sequester CO2 for long periods of time."

I suppose that the selected sites are carefully screen to prevent this, but I still don't see this as a permanent solution for geological time-scales. Some recent research papers suggest that we would need a much larger storage volume/CO2 volume ratio to prevent a Lake Nyos-type catastrophe, so our current estimates and degree of certainty may be off target.

Since the IPCC estimates that we can store 1,100,000 megatons of CO2 underground, I simply cannot see how we can be certain that catastrophic out-gassing amounts of only ~1 megaton will never happen.

Now, whether this risk is worth taking to help attenuate climate change is another story altogether...

To clarify, Lake Naos was a catastrophe because the CO2 was held under pressure only by the water column above it. Thus, once a small perturbation to that water column occurred, pressure decreased, resulting in the CO2 turning gaseous bubbling up. This in turn cause some more water to be displaced by splashing, further reducing the water column above the CO2, further reducing the pressure of the CO2, causing more CO2 to turn from liquid to gas and so on. Such a chain reaction would not occur with CO2 stored within subsurface sediments or rocks. The most likely scenario of upward leakage of CO2 would be a slow and small release, if any at all occurred. Such leakage could relatively easily be detected.

One of the more promising methods of detecting very small amounts of CO2 over large areal extents is by monitoring (from airplanes or satellites) very slight changes in the color of plants due to slight increases in CO2 content near their roots. This technology has been demonstrated successfully in the field. CO2 underground storage sites would have to, by law, be monitored extensively, so even in the unlikely event of a large-scale leak, it could be detected early and people evacuated (and unlike hazardous chemicals, nuclear radiation, or most any man-made industrial byproduct, the leaked CO2 would safely dissipate in a matter of days). I agree, leakage is definitely something to be concerned about, so careful analysis, preparation and regulation will be very important for any CO2 disposal approach.

Moreover, it should be forgotten that humans have stored very large amounts (greater than what has been proposed for CO2 storage) of gases and liquids in the subsurface (e.g., CO2 in enhanced oil recovery operations, sewage disposal, hazardous chemical disposal, temporary natural gas storage, general waste fluid storage, pressure energy storage). Nature has done so for millions of years in form of natural gas and even naturally occurring CO2.

Finally, the paper you linked, regarding limited storage volume, happens to be counter to the results of the vast majority of CO2 sequestration scientists (e.g., here and here).

To clarify, Lake Naos was a catastrophe because the CO2 was held under pressure only by the water column above it. Thus, once a small perturbation to that water column occurred, pressure decreased, resulting in the CO2 turning gaseous bubbling up. This in turn cause some more water to be displaced by splashing, further reducing the water column above the CO2, further reducing the pressure of the CO2, causing more CO2 to turn from liquid to gas and so on. Such a chain reaction would not occur with CO2 stored within subsurface sediments or rocks. The most likely scenario of upward leakage of CO2 would be a slow and small release, if any at all occurred. Such leakage could relatively easily be detected.

One of the more promising methods of detecting very small amounts of CO2 over large areal extents is by monitoring (from airplanes or satellites) very slight changes in the color of plants due to slight increases in CO2 content near their roots. This technology has been demonstrated successfully in the field. CO2 underground storage sites would have to, by law, be monitored extensively, so even in the unlikely event of a large-scale leak, it could be detected early and people evacuated (and unlike hazardous chemicals, nuclear radiation, or most any man-made industrial byproduct, the leaked CO2 would safely dissipate in a matter of days). I agree, leakage is definitely something to be concerned about, so careful analysis, preparation and regulation will be very important for any CO2 disposal approach.

Moreover, it should be forgotten that humans have stored very large amounts (greater than what has been proposed for CO2 storage) of gases and liquids in the subsurface (e.g., CO2 in enhanced oil recovery operations, sewage disposal, hazardous chemical disposal, temporary natural gas storage, general waste fluid storage, pressure energy storage). Nature has done so for millions of years in form of natural gas and even naturally occurring CO2.

Finally, the paper you linked, regarding limited storage volume, happens to be counter to the results of the vast majority of CO2 sequestration scientists (e.g., here and here).

Wow, it seems as though the Ehlig-Economides paper I linked to caused quite a stir in the geoscience community. After reading the rebuttals you provided, it does seem as though carbon capture and sequestration is tenable, at least for a while. Thanks for the explanations.

On the personal side, I noticed that you joined the Ars forum today and only talked about this subject. Do you by chance work in the geoscience/energy field? You seem to have the background knowledge, and I always appreciate when actual experts are able to contribute to the discussion.

It is actually VERY hard to seal Carbon Dioxide underground. It is even, I'm told, actually corrosive to material typically used to seal old oil wells. So the best way to put it anywhere is still to grow trees...

Jah, the whole carbon sequestration thang always did strike me as horseshit. First because it will leak, but more importantly, because the storage area wont even come close to the volume of co2 generated at today's massive scales, and especially because it would cost a fortune.

Totally agree with the previous commenter that the co2 in this case is a red Herring, being little more than a transfer fluid of limited and fixed quantity.

See other comments about potential leakage (which is actually quite unlikely). The amount of CO2 that can be geologically stored is far, far more than is produced, and the amount of CO2 is far less than other fluids we currently inject into the subsurface (see this publication). Right now, the US Geological Survey is undertaking a comprehensive assessment of all geologic formations in the US with the proper geology and structure to safely store CO2 in order to determine the potential storage volume -- detailed results will be out in about 2 years.

Geologic CO2 sequestration is the only technology that is viable or even close to viable for eliminating the massive amounts of anthropogenic atmospheric CO2 (see IPCC reports in 2005 and 2007). Unfortunately, there is nothing else even close to being an option in the next few decades, short of shutting down all CO2-producing power plants and parking all vehicles. So, we must decide whether to start implementing some sort of sequestration, while massively increasing construction of carbon neutral or negative energy systems, despite its relatively small risks or permit climate change to happen unchecked.

To clarify, Lake Naos was a catastrophe because the CO2 was held under pressure only by the water column above it. Thus, once a small perturbation to that water column occurred, pressure decreased, resulting in the CO2 turning gaseous bubbling up. This in turn cause some more water to be displaced by splashing, further reducing the water column above the CO2, further reducing the pressure of the CO2, causing more CO2 to turn from liquid to gas and so on. Such a chain reaction would not occur with CO2 stored within subsurface sediments or rocks. The most likely scenario of upward leakage of CO2 would be a slow and small release, if any at all occurred. Such leakage could relatively easily be detected.

One of the more promising methods of detecting very small amounts of CO2 over large areal extents is by monitoring (from airplanes or satellites) very slight changes in the color of plants due to slight increases in CO2 content near their roots. This technology has been demonstrated successfully in the field. CO2 underground storage sites would have to, by law, be monitored extensively, so even in the unlikely event of a large-scale leak, it could be detected early and people evacuated (and unlike hazardous chemicals, nuclear radiation, or most any man-made industrial byproduct, the leaked CO2 would safely dissipate in a matter of days). I agree, leakage is definitely something to be concerned about, so careful analysis, preparation and regulation will be very important for any CO2 disposal approach.

Moreover, it should be forgotten that humans have stored very large amounts (greater than what has been proposed for CO2 storage) of gases and liquids in the subsurface (e.g., CO2 in enhanced oil recovery operations, sewage disposal, hazardous chemical disposal, temporary natural gas storage, general waste fluid storage, pressure energy storage). Nature has done so for millions of years in form of natural gas and even naturally occurring CO2.

Finally, the paper you linked, regarding limited storage volume, happens to be counter to the results of the vast majority of CO2 sequestration scientists (e.g., here and here).

Wow, it seems as though the Ehlig-Economides paper I linked to caused quite a stir in the geoscience community. After reading the rebuttals you provided, it does seem as though carbon capture and sequestration is tenable, at least for a while. Thanks for the explanations.

On the personal side, I noticed that you joined the Ars forum today and only talked about this subject. Do you by chance work in the geoscience/energy field? You seem to have the background knowledge, and I always appreciate when actual experts are able to contribute to the discussion.

Thanks for all your excellent comments, they have really generated some nice discussion. As it happens, I am one of the authors of the report discussed in this article. Our article had to be quite short and, thus, could not include much of the information I provided in response to your comments. There was a lot more material that went into the thought and development of the report than made it into the final product. This site seems a great place to help provide people the background knowledge and access to additional information so they can make informed comments on new research and technology.

I'm hesitant of geothermal energy production. I could see if it became widely adopted we might create some kind of cooling effect in the crust. Maybe the opposite of Global warming it could be crustal cooling. I don't know what kind of effect this would have on plate tetonics or the magneto affect from the molten core. I know it wouldn't kill the molten core but it could slightly diminish its effects. Even a small change could have drastic affects.

Actually if life underground can use the CO2, with all that pressure and heat we are likely to get a a new fuel source where we can collect the converted biomass or biomass waste (biodiesel or methane?) and burn that in a carbon-neutral cycle. We'd have to be leery of ground water contamination though.

It is actually VERY hard to seal Carbon Dioxide underground. It is even, I'm told, actually corrosive to material typically used to seal old oil wells. So the best way to put it anywhere is still to grow trees...

Jah, the whole carbon sequestration thang always did strike me as horseshit. First because it will leak, but more importantly, because the storage area wont even come close to the volume of co2 generated at today's massive scales, and especially because it would cost a fortune.

Totally agree with the previous commenter that the co2 in this case is a red Herring, being little more than a transfer fluid of limited and fixed quantity.

See other comments about potential leakage (which is actually quite unlikely). The amount of CO2 that can be geologically stored is far, far more than is produced, and the amount of CO2 is far less than other fluids we currently inject into the subsurface (see this publication). Right now, the US Geological Survey is undertaking a comprehensive assessment of all geologic formations in the US with the proper geology and structure to safely store CO2 in order to determine the potential storage volume -- detailed results will be out in about 2 years.

Geologic CO2 sequestration is the only technology that is viable or even close to viable for eliminating the massive amounts of anthropogenic atmospheric CO2 (see IPCC reports in 2005 and 2007). Unfortunately, there is nothing else even close to being an option in the next few decades, short of shutting down all CO2-producing power plants and parking all vehicles. So, we must decide whether to start implementing some sort of sequestration, while massively increasing construction of carbon neutral or negative energy systems, despite its relatively small risks or permit climate change to happen unchecked.

Ok, I will back down and apologize for the use of the term "horseshit", seeing that I was wrong on the counts of storage capacity and the the risk of leaks, which I suppose is not worse than the risk of natural gas leakage (which does happen). AGW debating aside, I guess my main concern is the practicality of geological sequestration (the "fortune" part). How will sequestration be implemented on a large scale?

Energy costs from a power plant are projected to increase "30-60%" and require 25% more coal to be burnt in order to compress the CO2 for storage. The typical transport mechanism envisioned are CO2 pipelines. How much will it cost and how will the landscape look if every power plant has a pipeline connecting it to a geostorage facility? And even if the US (forget about China and developing countries) was criss-crossed with thousands of pipelines, it would only eliminate CO2 from point sources. It would not eliminate CO2 from cars and it would not scrub the existing atmosphere (as trees do). I just don't see this happening.

What happened to the computer model Ars trotted out to try and prove carbon capture is impossible when the oil and gas companies were doing it? Now when it's not an O&G suddenly carbon capture is feasible again? Says a lot about the politics rather than the balance of the coverage around here when it comes to GW.

Ok, I will back down and apologize for the use of the term "horseshit", seeing that I was wrong on the counts of storage capacity and the the risk of leaks, which I suppose is not worse than the risk of natural gas leakage (which does happen). AGW debating aside, I guess my main concern is the practicality of geological sequestration (the "fortune" part). How will sequestration be implemented on a large scale?

Energy costs from a power plant are projected to increase "30-60%" and require 25% more coal to be burnt in order to compress the CO2 for storage. The typical transport mechanism envisioned are CO2 pipelines. How much will it cost and how will the landscape look if every power plant has a pipeline connecting it to a geostorage facility? And even if the US (forget about China and developing countries) was criss-crossed with thousands of pipelines, it would only eliminate CO2 from point sources. It would not eliminate CO2 from cars and it would not scrub the existing atmosphere (as trees do). I just don't see this happening.

I imagine the plan would be to phase out carbon heavy power generation/transportation as much as possible and offset that with sustainable, carbon neutral alternatives. Where and when that isn't possible; I suspect you could gang geothermal power generation & carbon sequestration plants with carbon producing power plants to offset the carbon footprint of those remaining power plants.

As most climate scientists agree, there will be no one-size-fits-all solution to anthropomorphic climate change. It will take several approaches to address and remedy the situation. Unfortunately, the longer we sit on our hands or wave them wildly around defending the status quo (<-- not directed at you personally), the less time we have to mitigate the effects of anthropomorphic climate change.

What happened to the computer model Ars trotted out to try and prove carbon capture is impossible when the oil and gas companies were doing it? Now when it's not an O&G suddenly carbon capture is feasible again? Says a lot about the politics rather than the balance of the coverage around here when it comes to GW.

While Dr. Shaffer considered sequestration independently, it may be most effective if used in tandem with lowering carbon emissions in general. Still, his research suggests that at least some monitoring of any sequestration approach would be in order if we decide to commit to it, to ensure that the containers don't end up sneakily working against us.

The take away from that paragraph is that carbon sequestration is not a solution in and of itself. We can't sequester carbon while continuing to pump out the same amount (or more) of carbon into atmosphere as we do now.

It is actually VERY hard to seal Carbon Dioxide underground. It is even, I'm told, actually corrosive to material typically used to seal old oil wells. So the best way to put it anywhere is still to grow trees...

Jah, the whole carbon sequestration thang always did strike me as horseshit. First because it will leak, but more importantly, because the storage area wont even come close to the volume of co2 generated at today's massive scales, and especially because it would cost a fortune.

Totally agree with the previous commenter that the co2 in this case is a red Herring, being little more than a transfer fluid of limited and fixed quantity.

See other comments about potential leakage (which is actually quite unlikely). The amount of CO2 that can be geologically stored is far, far more than is produced, and the amount of CO2 is far less than other fluids we currently inject into the subsurface (see this publication). Right now, the US Geological Survey is undertaking a comprehensive assessment of all geologic formations in the US with the proper geology and structure to safely store CO2 in order to determine the potential storage volume -- detailed results will be out in about 2 years.

Geologic CO2 sequestration is the only technology that is viable or even close to viable for eliminating the massive amounts of anthropogenic atmospheric CO2 (see IPCC reports in 2005 and 2007). Unfortunately, there is nothing else even close to being an option in the next few decades, short of shutting down all CO2-producing power plants and parking all vehicles. So, we must decide whether to start implementing some sort of sequestration, while massively increasing construction of carbon neutral or negative energy systems, despite its relatively small risks or permit climate change to happen unchecked.

Ok, I will back down and apologize for the use of the term "horseshit", seeing that I was wrong on the counts of storage capacity and the the risk of leaks, which I suppose is not worse than the risk of natural gas leakage (which does happen). AGW debating aside, I guess my main concern is the practicality of geological sequestration (the "fortune" part). How will sequestration be implemented on a large scale?

Energy costs from a power plant are projected to increase "30-60%" and require 25% more coal to be burnt in order to compress the CO2 for storage. The typical transport mechanism envisioned are CO2 pipelines. How much will it cost and how will the landscape look if every power plant has a pipeline connecting it to a geostorage facility? And even if the US (forget about China and developing countries) was criss-crossed with thousands of pipelines, it would only eliminate CO2 from point sources. It would not eliminate CO2 from cars and it would not scrub the existing atmosphere (as trees do). I just don't see this happening.

You ask very good questions, questions that many scientists, economists, etc. are working to answer. Concerning cost, most of the cost (80%) associated with carbon capture and sequestration is on the capture side, right at the emitters. This cost will come down as technology improves (this is a huge field of research). Importantly, though, coal power plants are the most expensive places to capture CO2 because the flue gas stream is quite dilute (~10% CO2). As capture technology develops, it makes more sense to at first capture from easier, significantly cheaper targets: natural gas power plants (~20% CO2 flue gas stream) and biofuel plants (~90% CO2 waste gas stream).

The US already has hundreds of thousands of miles of pipelines (e.g., see page 48 of the Final Report here), including many CO2 pipelines. Much of the challenge with building a pipeline is obtaining the land right-of-ways. However, it's relatively easy to build an additional pipeline alongside one that already exists (such as to natural gas power plants, or to oil and gas fields -- which would be excellent CO2 sequestration sites).

It is also possible to capture CO2 directly from the air (e.g., this Department of Energy report), avoiding both piping and the inability of conventional CO2 capture to collect CO2 from non-point sources. If we really want to avoid anthropogenic CO2 release to the atmosphere, some major technological and lifestyle changes will likely be required. To minimize non-point CO2 sources, we may need to switch to electric and biofuel vehicles (cellulosic ethanol and biodiesel).

With any sort of fee on carbon emissions, CO2 capture and storage quickly becomes very economical. Just a few decades ago, our waterways were places that sewage and industrial wastes could be freely dumped. Yet these days, few in the general populace would be ok with minimally-regulated dumping of known pollutants into our waterways. Soon, with all the major atmospheric pollutants (not just mercury, sulfur dioxide, etc) we need to follow our own example.

I'm hesitant of geothermal energy production. I could see if it became widely adopted we might create some kind of cooling effect in the crust. Maybe the opposite of Global warming it could be crustal cooling. I don't know what kind of effect this would have on plate tetonics or the magneto affect from the molten core. I know it wouldn't kill the molten core but it could slightly diminish its effects. Even a small change could have drastic affects.

Geothermal production is unlikely to extend below 10km below the surface (5km is stretching it, even), whereas the continental crust is on average 40km thick. Thus, it's highly unlikely that the deep crust or any other part of the planet, where plate tectonics and deeper processes are governed, could be affected. Geothermal systems could only harness a tiny portion of the earth's heat (essentially equivalent to the fraction of all sunlight that could be harvested by solar panels), so planet-scale properties are unlikely to be affected.

That said, like any power source, geothermal can have temporary local effects. For instance, we wouldn't harness heat from under Yellowstone because its geysers might stop functioning for a time (because heat would be diverted from the geysers to the power plant). Any site for any kind of power production must be carefully studied in order to avoid negative effects.